DE102009027015A1 - Method for determining rotational speed of starter-motor for internal combustion engine in motor vehicle, involves calculating rotational speed of machine from electrical parameters, and executing calibration of rotational speed - Google Patents

Abstract

The method involves energizing an armature via a commutator by using brushes, where rotational speed of a direct current machine i.e. starter-motor (2), is calculated from electrical parameters. Calibration of the rotational speed is executed. The rotational speed is derived from a rotational speed constant and voltage induced in the armature during an operation of the direct current machine. The induced voltage is derived from brush resistance and armature resistance at temporarily defined, specific time points. Independent claims are also included for the following: (1) a controller for an electrical machine such as direct current machine i.e. starter-motor, for an internal combustion engine in a motor vehicle, comprising a measuring and evaluating device (2) a computer program product having a set of instructions to perform a method for determining rotational speed of an electrical machine such as direct current machine i.e. starter-motor, for an internal combustion engine in a motor vehicle.

Description

State of the art

The The invention relates to methods for determining a speed an electrical machine, in particular a DC machine with an armature, a commutator and brushes for energizing of the armature via the commutator, with the speed off electrical quantities is calculated. The invention further relates to a controller for such DC machine, the controller with a measuring and evaluation for calculating a speed of the DC machine is formed of electrical quantities.

A Internal combustion engine in a motor vehicle usually becomes started with a starter, a DC machine as a starter motor and having a starter pinion in a sprocket with the internal combustion engine is coupled to start this.

at known start-stop systems, it is according to special Methods and embodiments that are desirable Internal combustion engine in many situations as quickly as possible to start, in particular, a leaking internal combustion engine should be started without a stoppage of the internal combustion engine to be seen. For this purpose, the starter pinion of the starter motor is possible coupled in synchronism with the internal combustion engine by the starter pinion is synchronized synchronously in the ring gear, in order thus a low-noise and low-wear meshing too guarantee. For this, the speed of the starter motor and also detects a speed of the crankshaft. A speed detection the starter motor is at a cold start of the engine not mandatory. The knowledge of the speed is only in start-stop mode important to synchronously einzuspuren in the leakage of the internal combustion engine.

The Speed of a DC machine, for example, with a Speed sensor can be determined. For brushed DC machines can also increase the speed of the armature electrical quantities are calculated.

The DE 10 2006 039 112 A1 describes a method for determining the rotational speed of a starter motor by means of a calculation algorithm from the electrical quantities in the power supply of the motor, namely a terminal voltage and an armature current.

It Object of the invention, a method, a controller and a Computer program product of the type mentioned in such a way that a determination of the speed of a DC machine, in particular for a start-stop operation of the internal combustion engine, improved becomes.

Disclosure of the invention

According to the invention the object by the subject-matter of claims 1, 2, 10 and 12 solved. The dependent claims define preferred developments of the invention.

One important aspect of the invention resides in a calibration To determine characteristics of the DC machine, that of a more accurate speed determination from electrical quantities serve the machine. Thus, the current state of the DC machine, at least at the time of calibration, for speed determination taken into account, in particular aging and temperature influences or also manufacturing tolerances of the DC machine. By the Calibration will be the accuracy in determining the speed increased, the accuracy especially in comparison to a conventional determination of the parameters, for example, according to a mathematical model or according to characteristic values, which were determined before or during the manufacture of the DC machine, is increased.

there The invention is preferably directed to a DC machine in a motor vehicle, in particular a starter motor of a start-stop system with an internal combustion engine because there is external Influences, especially due to changing temperatures or by aging, the DC machine is interacting. So it will be especially during start-stop operation characteristics determined by the starter motor and then the speed of the DC machine or the starter motor calibrated or calculated.

Preferably in connection with the above-mentioned aspect, but also independently thereof, a further aspect of the invention resides in that the rotational speed is derived from a voltage induced in the armature during operation of the DC machine and a rotational speed constant. Thus, material and assembly costs, and costs for a speed sensor can be saved. The induced voltage is generated during a rotational movement of the rotor in a magnetic field of a stator of the DC machine and is essentially dependent on the strength of the magnetic field, the rotational speed of the rotor and the mechanical structure of the DC machine, in particular a coil winding of the armature, as well as their temperature. Thus, the accuracy for determining the speed is increased because the induced voltage depends directly on the speed and in particular is proportional to this.

The The speed constant can be before or during production the DC machine is determined or calculated or off derived from a mathematical model.

Preferably is the speed constant by the inventive Calibration determined, ie as soon as possible to the determination the speed. So with the speed constants a current information about the DC machine won and an accurate determination of their speed allows.

The The object underlying the invention is particularly by solved a control for the DC machine, that a measuring and evaluation device for determining the at Operation of the DC machine in the armature induced voltage and for calculating the speed from the induced voltage and the speed constant is formed, preferably after one of the methods mentioned above or below.

It is preferred that the controller for a starter of Internal combustion engine is designed in a motor vehicle, wherein the Starter and the internal combustion engine at a leaking internal combustion engine be coupled with a starter pinion in a sprocket, and the Control is designed to reduce the speed of the starter motor, in particular according to a method mentioned above or below, to determine the starter pinion in the sprocket substantially synchronously einzuspuren. So is a low-wear as possible and quiet coupling of the starter and the internal combustion engine achieved.

As previously mentioned, a still expiring internal combustion engine can be started become. For this purpose, the speed of the starter motor increases increasingly to couple the starter and the engine as soon as possible the starter pinion and the ring gear are essentially synchronous. Alternatively, the starter or the starter motor to a certain Speed can be accelerated to then the expiring Starter and the expiring internal combustion engine to couple once the starter pinion and the ring gear are essentially synchronous. In both methods for coupling the starter and the internal combustion engine So is the speed of the starter motor after a previous or subsequent The method specified for the synchronous meshing of the starter pinion to allow in the sprocket.

Preferably The induced voltage is also a brush resistance and an anchor resistance, in particular to temporarily defined, certain times, derived. The induced voltage is measured only at the times when the speed is determined, so a continuous detection of the induced voltage is not is preferred. Two measurements of the induced voltage and the determination two speeds can be consecutive, for example in the range of milliseconds, so that also an acceleration can be determined more accurately from the speeds. The anchor resistance is essentially by the formation of the anchor, in particular one Armature winding, determined. The anchor resistance changed over the life only marginally and has one known and predictable temperature dependence. The brush resistance is preferably determined by the aforementioned calibration. Thus, the important, the DC machine characterizing Characteristics brush resistance and armature resistance taken into account and the accuracy in determining the Speed increased.

at In a preferred embodiment, the speed constant determined during idle operation of the DC machine. While idle mode, the DC machine is unloaded and the Speed constant more accurately determinable, ultimately the accuracy in determining the speed of the loaded DC machine to increase.

The Speed constant is preferably from an idle speed of DC machine and thereby induced in the armature induced voltage, as a quotient of this induced voltage and the idle speed can be calculated. In this case, the idling speed is preferably Derived from a commutation frequency, the design of the Commutator, in particular the number of Kommutatorkontakte to take into account.

The Commutation frequency can be from a terminal voltage, so the the terminals of the DC machine voltage, can be obtained by preferably using a bandpass filter is to filter out the so-called Rippelfrequenz, so one Modulation of the terminal voltage caused by the discontinuous Energizing the armature by means of the brushes and the commutator caused.

In this embodiment, the commutation frequency is preferably determined in idle mode, wherein the idle speed of the unloaded DC machine is essentially conditioned by their construction and thus known. Then a simple, sufficient for the expected ripple frequency trained band is sufficient Pass filter with fixed cut-off frequencies to determine the idle speed from the terminal voltage. In particular, no costly adaptation of the bandpass filter to different speed ranges is necessary.

The induced voltage can therefore, as mentioned above, both for the determination the speed of the DC machine, especially under load, as well as for determining the speed constants, in particular at an idling operation, are determined. It is for the determination the induced voltage is preferably the terminal voltage and the Armature current, in particular with the measuring and evaluation device, measured. The terminal voltage can be calculated as the sum of different partial voltages, namely the induced voltage, one above the Anchor dropping voltage and one above the commutation system declining voltage, so that the induced Voltage from the difference between the terminal voltage and the sum of over the anchor and falling over the commutation system Tension is determinable.

The above the voltage dropping off the armature can be instantaneous from the strength a current through the DC machine equal to the armature current is derived and the armature resistance. Analogously, the over the commutation system sloping voltage from the stream, ie also the armature current, and the resistance of the commutation system, previously and subsequently called brush resistance derived become.

at a further embodiment, as mentioned above, the brush resistance determined by the calibration, and preferably on the unloaded DC machine.

there It is particularly preferred that the unloaded DC machine is energized with an armature current, a terminal voltage at this Current is measured, the energization, preferably briefly, is interrupted, another terminal voltage at a pure generator operation of the DC machine is measured and the brush resistance from the two measured terminal voltages and the armature current is derived. This is the brush resistance simple and inexpensive, namely by measuring of terminal voltages and armature current. The respective Brush resistance is the quotient of a difference the terminal voltages and the armature current calculated, the terminal voltage in the pure generator operation of the terminal voltage at the current is subtracted. Due to aging respectively Brush wear changes the brush resistance is irregular and unpredictable, so that by the calibration of a current Brush resistance for a more accurate speed detection is determined.

at This embodiment is also preferred that the unloaded DC machine with at least two, preferably three or four, different armature currents is energized and each of the Brush resistance for the respective current supply like previously described. As the brush resistance is dependent on the current, it becomes so for different Currents determined to the induced voltage and ultimately to more accurately determine the speed of the DC machine.

The so determined different brush resistance at different armature currents serve as support points preferably for a polynomial function or alternatively by means of Interpolation for a determination of the speed at any Intermediate values of these currents and thus increase a calculation accuracy of the speed determination.

All in all So allows the calibration, the speed constant and / or the brush resistance, in particular a Current dependence of the brush resistance or a plurality of brush resistors, that is, different ones Resistance values of the commutation system, at different Anchor currents to determine.

Especially Preferably, the calibration is done by the DC machine is accelerated to its idle speed, the acceleration phase, especially several times at different current levels, is interrupted to, respectively, a brush resistance to determine at a certain amperage, and after that Reaching the idling speed, the speed constant is determined.

in the Trapping a starter motor as a DC machine becomes the calibration preferably performed during operation of the internal combustion engine, noises of the idling starter due to noise to cover the internal combustion engine. It is also preferred that the calibration at least 1500 revolutions per minute of the internal combustion engine is started, so ensured is that the starter is not immediately to start the engine is needed.

Preferably, in particular in a start-stop system, the calibration of the starter motor according to the invention is carried out after each start of the internal combustion engine, in each case by current, in particular temperature-dependent, information, the accuracy of the speed determination to increase. The calibration can be done as soon as possible after the startup, since at such time the starter is not needed for another boot process.

The The object underlying the invention is also solved by a computer program product, that into a memory with program commands from a microcomputer loadable to carry out a previously described method, especially if the program is in one of the previously described Controls is running.

It It is understood that the above and below to be explained features not only in the specified Combination, but also usable in other combinations.

Brief description of the drawings

The Invention will be described below with reference to the drawings explained in more detail. Show it:

1 a schematic representation of a starting device with a controller according to the invention for a DC machine,

2 a schematic equivalent circuit diagram of a DC machine,

3 Method steps for calibrating a brush resistance,

4 a schematic representation of the startup of a starter motor,

5 a current dependence of a brush resistance,

6 a frequency spectrum of a terminal voltage of a DC machine and

7 a schematic representation of speeds when coupling a starter and an internal combustion engine.

embodiments the invention

The 1 shows a schematic representation of a starting device according to the invention with a controller 1 for a DC machine, designed as a DC machine starter motor 2 for an internal combustion engine 3 in a motor vehicle and a battery 11 as a power source. The starter motor 2 is by means of a starter pinion 4 in a sprocket 5 from the internal combustion engine 3 einspurbar. The starter motor 2 has a rotor, not shown, with an armature and a commutator, which by means of brushes via the terminals 6 from the controller 1 is energized. The starter with the starter motor 2 and the controller 1 are designed as a start-stop system in which the internal combustion engine 3 is stopped during a brief stoppage of the motor vehicle and as soon as possible restarted for further travel of the motor vehicle with the starting device. In order to increase the availability, in particular according to special operating modes, in an expiring internal combustion engine 3 meshed, without a stoppage of the internal combustion engine 3 to be seen. This is the starter pinion 4 essentially with synchronously running peripheral speeds in the sprocket 5 eingepurt, where for a low noise and low wear meshing in the rotating sprocket 5 the expiring internal combustion engine 3 the speed of the starter motor 2 as described below is recorded as accurately as possible.

The control 1 has a measuring and evaluation device 7 for determining the speed of the starter motor 2 with a microcomputer 8th and with a memory 9 on, so that the above and below mentioned method steps using a computer program product, which in the memory 9 with program commands of the microcomputer 8th is loaded. For speed detection is with a measuring device 10 the terminal voltage U _Kl , that is the over the terminals 6 the starter motor 2 decreasing voltage, and the armature current I _{A of} the starter motor 2 determines and from these electrical variables, the speed n of the starter motor 2 from the measuring and evaluation device 7 calculated what's in detail with the following 2 is explained.

The 2 shows a schematic equivalent circuit diagram of the starter motor 2 with the terminals 6 and a series circuit of a so-called brush resistor R _B , that is a resistance of the commutation of the commutator and the brush, an armature resistance R _A , an inductance L _{A of} the armature winding and a source of the induced voltage U _ind . The induced voltage U _ind is due to the rotational movement of the rotor, in particular the winding of the armature, in a magnetic field of the stator, also not shown, and is proportional to the speed n of the starter motor 2 So the rotor. In this case, the induced voltage U _{ind is associated} with the rotational speed n via a rotational speed constant Φ (T) which serves as a proportionality factor and which takes into account, in particular, a field of excitation of permanent magnets of the stator, wherein the rotational speed constant Φ (T) depends in particular on a temperature T, but also aging-related effects of the starter motor 2 considered. Overall, the speed n as a quotient of the induced voltage U _ind and the speed constant Φ (T) is calculated. In this case, the induced voltage U _ind according to the equivalent circuit diagram after 2 calculated from the measured terminal voltage U _Kl by the above the brush resistance R _B and the armature resistance R _A falling voltages are subtracted, which are in turn next to the resistance values determined by the also measured armature current I _A , so that the formula U _ind = U _Kl - I _A · (R _B + R _A ). In this case, the armature resistance R _A by the construction of the starter motor 2 , In particular, the armature winding, and its temperature dependence known, with its value changes only insignificantly over the life. The brush resistance R _B is in particular also dependent on a current through the commutation system, that is, as it were, also the armature current I _A. The speed constant Φ (T) is dependent on temperature and age, wherein in particular the magnetic field of the stator is temperature and aging dependent.

The brush resistance R _B and the speed constant Φ (T) are conventionally calculated according to a mathematical model, in particular a formula, or read out as values from a memory, but in particular age-related effects and further influences on the starter motor 2 can not be considered accurately. Therefore, in this embodiment, both variables, namely the brush resistance R _B and the speed constant Φ (T), as described below, are determined by a calibration closer.

It is preferred to calibrate after each starting operation of the internal combustion engine 3 performed, and indeed, when the internal combustion engine 3 running at least 1500 revolutions per minute to ensure that in the next few moments the starter motor is not required for a startup operation and a starter noise when calibrated by the noise of the engine 3 to cover.

During calibration, two variables are calibrated, namely the brush resistance R _B during a start-up of the starter motor 2 and then the speed constant Φ (T) in a run-up state, ie at an idling speed of the starter motor 2 , where the calibration with the unloaded starter motor 2 , so without the starter pinion 4 in the sprocket 5 , is carried out.

The 3 shows process steps for calibrating the brush resistance R _B when starting the starter motor 2 , First, the starter motor 2 from the controller 1 driven. In this case, the armature current I _A in one step 30 and the over the terminals 6 decreasing voltage U _on with energized current in one step 31 from the measuring device 10 measured. In one step 32 the energization is interrupted very briefly during startup, and in the case of interrupted energization, that is to say in the case of pure generator operation of the starter motor 2 , which is above the terminals 6 decreasing voltage U _out induced in the armature in one step 33 from the measuring device 10 measured. From these electrical quantities U _an , U _out , I _A is in one step 34 the brush resistance R _B as a function of the measured armature current 1A calculated according to the equation R _B = (U _an -U _out ) / I _A.

The startup of the starter motor 2 will, as in the 4 shown at three different armature currents respectively for in the 3 interrupted process steps so as to determine the current dependence of the brush resistance R _B.

The 4 shows a schematic representation of the startup of the starter motor 2 over time t. Plotted are the armature current I _A and the over the terminals 6 decreasing voltages U _on and U _off when energized or switched off. In each case at the times t ₁ , t ₂ , t ₃ , ie at the armature currents I ₁ , I ₂ , I ₃ , the brush resistors R _B1 , R _B2 and R _{B3 will be} dependent on the armature currents I ₁ , I ₂ , I ₃ determined and in the memory 9 of the microcomputer 8th saved as a table

In this embodiment, in the calculation of the rotational speed n at a certain armature current I _{A of} the respective brush resistance R _B based on in the 5 shown function course 50 determined by extrapolation beyond I ₁ and I ₃ and by interpolation between the brush resistances R _B1 , R _B2 , R _B3 detected by the calibration.

The 6 shows a measuring signal 43 , namely a frequency spectrum that is out of the over the terminals 6 decreasing voltage is obtained during the calibration. As previously explained, the starter motor will be used for calibration 2 in a first period 40 ramped up, so accelerated to a second period 41 at idle speed n _empty to determine the speed constant Φ (T). Then the starter motor is running 2 in the period 42 out. Here is the measurement signal 43 with an unloaded starter motor 2 has been measured, for clarity, the above-described interruptions for determining the brush resistance R _B during startup during the period 40 are not shown. The measuring signal 43 is the so-called Rippelfrequenz, so a modulation of the terminals 6 decreasing voltage due to the commutation of the rotor with the brushes, again, which is measured by means of at least one of the idling speed n _empty tuned bandpass filter, namely with at least one simple, preferably fixed bandpass filter, in particular with fixed cut-off frequencies, since the idling speed n is _{empty of} the unloaded starter motor 2 is known.

From the ripple frequency, which still depends on the number of contacts of the commutator in addition to the speed of the rotor, is of the measuring and evaluation 7 So directly idle speed n determined _empty . With this information, as previously described, the speed constant Φ (T) is calculated _empty according to the formula Φ (T) = U _ind / n, wherein the induced voltage U _ind during calibration, ie during idling in the period 41 , as described above, from measurements of the terminal voltage U _Kl and the armature current I _{A is} calculated.

Overall, the controller 1 So at any time the speed n of the starter motor 2 from the terminal voltage U _Kl and the armature current I _A with the aid of the values known from the calibration of the brush resistance R _B and the speed constant Φ (T), as well as the known armature resistance R _A according to the formula n = U _ind / Φ (T) = ( Calculate U _Kl - I _A (R _B + R _A )) / Φ (T).

The 7 shows two further embodiments, each with alternative methods for coupling the starter according to the first embodiment with the internal combustion engine 3 , The show 7a and the 7b one speed each 70 of the sprocket 5 caused by the leaking internal combustion engine 3 is determined, and a speed 71 of the starter pinion 4 , by the speed of the starter motor 2 is determined, wherein the speed of the starter motor 2 determined as described above.

In the in the 7a illustrated embodiment, the starter motor 2 in a run-up phase 72 accelerated, then turned off, so that the speed 71 of the starter pinion 4 in a phase out 73 drops. Because the starter motor 2 and the internal combustion engine leak at different speeds, the shows 7a an intersection of the speeds 70 . 71 , which on the time axis t a Einspurpunkt 74 marked, to which the starter pinion 4 in the sprocket 5 synchronized synchronously.

The 7b shows a method for faster starting of the internal combustion engine 3 , This is the starter pinion 4 in the sprocket 5 harnessed by during a startup phase 72 the speed 71 of the starter pinion 4 at the speed 70 of the sprocket 5 is compared by the speed n of the starter motor 2 as previously described. This will be the starter pinion 4 and the sprocket 5 meshed as soon as they synchronous speeds 70 . 71 to reach.

Overall, by the invention, the accuracy in determining the speed n of the starter motor 2 increase. It can in particular temperature and aging effects continuously, so for example after each startup of the internal combustion engine 3 , determined and taken into account in the calculation of the speed n. In addition, the invention allows a quick startup process by a still expiring internal combustion engine 3 through synchronous meshing of the starter pinion 4 in the sprocket 5 is started with low noise and wear. All figures show only schematic not to scale representations. Moreover, reference is made in particular to the drawings for the invention as essential.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102006039112 A1 [0005]

Claims (12)

Method for determining a rotational speed (n) of an electrical machine, in particular a DC machine, in particular a starter motor ( 2 ) for an internal combustion engine ( 3 ) in a motor vehicle, with an armature, a commutator and brushes for energizing the armature via the commutator, wherein the rotational speed (n) is calculated from electrical quantities, characterized in that a calibration of the rotational speed (n) is performed. Method for determining a rotational speed (n), in particular according to Claim 1, of a DC machine, in particular of a starter motor ( 2 ) for an internal combustion engine ( 3 ) in a motor vehicle, with an armature, a commutator and brushes for energizing the armature via the commutator, wherein the speed (n) is calculated from electrical quantities, characterized in that the speed (n) from a during operation of the DC machine in the Anchor induced voltage (U _ind ) and a speed constant (Φ (T)) is derived. Method according to one of claims 1 to 2, characterized in that the induced voltage (U _ind ) from a brush resistor (R _B ) and an armature resistor (R _A ), in particular at temporarily defined, certain times, is derived. Method according to one of claims 1 to 3, characterized in that the speed constant (Φ (T)) in an idling operation of the DC machine, in particular during operation of the internal combustion engine ( 3 ). A method according to claim 4, characterized in that a commutation frequency from the terminal voltage (U _Kl ) of the DC machine is determined from the commutation frequency an idle speed (n _empty ) is derived and the speed constant (Φ (T)) from the induced voltage (U _ind ) and the idle speed (n _empty ) is derived. Method according to one of claims 1 to 5, characterized in that a brush resistor (R _B ) during energization of the unloaded DC machine, in particular during operation of the internal combustion engine ( 3 ). A method according to claim 6, characterized in that the unloaded DC machine is energized with an armature current (I _A ), a terminal voltage (U _on ) is measured during energization, the energization is interrupted, another terminal voltage _{( Usus )} in a purely regenerative operation the DC machine is measured and the brush resistance (R _B ) is derived from the measured terminal voltages (U _in , U _out ) and the armature current (I _A ). A method according to claim 6, characterized in that the unloaded DC machine with at least two different armature currents (I ₁ , I ₂ , I ₃ ) is energized and in each case a brush resistance (R _B1 , R _B2 , R _B3 ) determined according to the method of claim 6 becomes. Method according to one of claims 1 to 7, characterized in that the speed constant (Φ (T)) and / or the brush resistance (R _B ) after each start of the internal combustion engine ( 3 ) is determined. Control ( 1 ) for an electrical machine, in particular a DC machine, in particular a starter motor ( 2 ) for an internal combustion engine ( 3 ) in a motor vehicle, with an armature, a commutator and brushes for energizing the armature via the commutator, wherein the controller ( 1 ) for the calculation of a speed (n) of the direct current machine from electrical quantities with a measuring and evaluation device ( 7 ), characterized in that the measuring and evaluation device ( 7 ) for determining a voltage induced in the armature during operation of the DC machine (U _ind ) and for calculating the speed (n) from the induced voltage (U _ind ) and a speed constant (Φ (T)), in particular for carrying out a method according to one or more of claims 1 to 9. Control ( 1 ) according to claim 10, characterized in that the controller ( 1 ) for a starter of an internal combustion engine ( 3 ) is designed in a motor vehicle, wherein the starter and the internal combustion engine ( 3 ) in an outgoing internal combustion engine ( 3 ) with a starter pinion ( 4 ) in a sprocket ( 5 ) and the controller ( 1 ) is adapted to a speed (s) of the starter motor ( 2 ), in particular according to a method according to one or more of the preceding claims 1 to 9, to determine the starter pinion ( 4 ) in the sprocket ( 5 ) essentially synchronously. Computer program product stored in a memory ( 9 ) with program commands from a microcomputer ( 8th ) in order to carry out at least one method according to one of Claims 1 to 9, when the program is stored in an electronic control system ( 1 ) is carried out according to one of claims 10 and 11.